Get rid of ZoneScope completely.

src/hydrogen-environment-liveness.h

 // Copyright 2013 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 44 matching lines @@
   void ZapEnvironmentSlotsForInstruction(HEnvironmentMarker* marker);
   void UpdateLivenessAtBlockEnd(HBasicBlock* block, BitVector* live);
   void UpdateLivenessAtInstruction(HInstruction* instr, BitVector* live);
 
   Zone* zone() { return &zone_; }
 
   HGraph* graph_;
   // Use a dedicated Zone for this phase, with a ZoneScope to ensure it
   // gets freed.
   Zone zone_;
-  ZoneScope zone_scope_;
 
   int block_count_;
 
   // Largest number of local variables in any environment in the graph
   // (including inlined environments).
   int maximum_environment_size_;
 
   // Per-block data. All these lists are indexed by block_id.
   ZoneList<BitVector*>* live_at_block_start_;
   ZoneList<HSimulate*>* first_simulate_;
   ZoneList<BitVector*>* first_simulate_invalid_for_index_;
 
   // List of all HEnvironmentMarker instructions for quick iteration/deletion.
   // It is populated during the first pass over the graph, controlled by
   // |collect_markers_|.
   ZoneList<HEnvironmentMarker*>* markers_;
   bool collect_markers_;
 
   // Keeps track of the last simulate seen, as well as the environment slots
   // for which a new live range has started since (so they must not be zapped
   // in that simulate when the end of another live range of theirs is found).
   HSimulate* last_simulate_;
   BitVector* went_live_since_last_simulate_;
 };
 
 
 } }  // namespace v8::internal
 
 #endif /* V8_HYDROGEN_ENVIRONMENT_LIVENESS_H_ */